الفهرس 
Introduction
Neuroanatomical backgroundOnly 14 pages are availabe for public view
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Abstract
Atherosclerosis is a major cause of ischemic stroke and a significant proportion of strokes are thromboembolic in nature, arising from atherosclerotic plaques(1).. In the United States and Western communities, extra-cranial carotid artery disease was estimated to be responsible for 20—30% of strokes (2-4). Little is known about the prevalence and distribution of carotid disease among the populations in the developing countries. Vascular duplex ultrasonography is a useful, cheap and available diagnostic tool for assessing cranial vascular disease. Duplex US can be highly reliable with proper technique, without the risk of radiation in other imaging modalities, is well tolerated by all patients including those who are claustrophobic in MRI machines, and has much less risks compared to conventional angiography studies(5). The purpose of the study is providing normal duplex parameters of extra cranial neck vessels. Our study includes 100 apparently healthy subjects, 56 females and 44 males, their ages ranged from 20 to 60 years old, who are resident doctors, nursing staff, coworkers and healthy relatives of the patients during the period from December 2017 to July 2019. The study was approved by ethics committee of faculty of medicine, assiut university. History and clinical examination suggestive of central and peripheral vascular disease is carried out to exclude any case with past history of vascular diseases. Blood pressure and random blood glucose measurements are done to exclude hypertensive and diabetic patients. Also, smokers have been excluded from this study. Inclusion criteria in the studied cases: Cases with age from 20 to 60 years oldCases using moderate amount of salt per day Cases having moderate amount of caffeine per day Both sexes are included Exclusion criteria in the studied cases: Diabetic patientsHypertensive patientsPeople with hyperlipidemic disordersPeople with hyperuricemia Smokers Cases with vascular diseases (central, peripheral and cardiac vascular diseases) Cases using Vasoactive medications Refusal of the cases to participate in the study Sample Size Calculation: 100 subjects divided between both sexes equally and along the age groups as follows 20 < 30 years: 25 subjects 30 < 40 years: 25 subjects 40 < 50 years: 25 subjects 50 < 60 years: 25 subjects DOCUMENTATION: Duplex evaluation is performed bilaterally starting with the right side. Long axis B-mode images to be obtained from: Common carotid artery (CCA) Carotid artery bifurcation (if both the internal carotid artery (ICA) and the external carotid artery (ECA) are not visible in one image, take an image of each with the bifurcation) Internal carotid artery (ICA) Spectral Doppler waveforms and velocity measurements must be documented from: Proximal CCA peak systolic velocity (PSV) Mid CCA PSV Proximal ICA PSV and end diastolic velocity (EDV) Mid ICA PSV and EDV if stenosis is present Distal ICA PSV and EDV ECA PSV (temporal tap may be used to identify) Vertebral Artery PSV The ICA/CCA ratio should be calculated using a normal CCA PSV and the highest ICA PSV. The results of the present study show no statistically significant difference between the studied male subjects and the female ones regarding the mean age in years, weight in kilograms and height in centimeters. In this study, it was found that the Intimal medial thickness of the common carotid arteries increases with advancing age. While there is no significant change in the intimal medial thickness in relation to sex. Also, the intimal medial thickness in the common carotid is found to increase as the body mass index and body weight increases (directly related). There is significant difference is found in the peak systolic velocity (PSV) of the common carotid arteries in the form of being higher in males of the same age group than in female ones. Both resistance index (RI) and pulsitility index (PI) of the common carotid artery are found to significantly higher in younger group compared to older group (inverse relation with age). Regarding the internal carotid artery, it was found that all parameters are higher in young group compared to older one (inverse relation with age). With peak systolic velocity is significantly higher in younger group compared to older one. The internal carotid artery duplex parameters are higher in females compared to males this is in accordance with the fact that the cerebral blood flow is higher in females than in males. Also, the ratio of mean of the duplex parameters in the internal carotid artery with the common carotid artery with peak systolic velocity is higher in females than males and the reverse is found in relation to the end diastolic velocity. Regarding the external carotid artery, all parameters higher in younger males than in older females (inverse relation with age). Regarding the extracranial vertebral system, no significant difference is found in all duplex parameters regarding age and sex except for the vertebral artery diameter which is significantly higher in males compared to females. Regarding the middle cerebral artery, it was found that the peak systolic velocity and end diastolic velocity are higher in younger females than in older males (inverse relation with age).